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首页> 外文期刊>Journal of geodynamics >Time evolution of negative buoyancy of an oceanic slab subducting with varying velocity
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Time evolution of negative buoyancy of an oceanic slab subducting with varying velocity

机译：速度变化的大洋板俯冲负浮力的时间演化

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摘要

The negative buoyancy of a subducting oceanic slab is estimated based on thermal models and various kinematic boundary conditions. Both temperature and negative buoyancy are time-dependent and are computed subject to time-varying subduction rates. The magnitude of the negative buoyancy increases with increasing depth of penetration of the slab and subduction velocity. For mature oceanic lithosphere, the buoyancy of a slab reaching the base of the mantle transition zone is approximately 5 x 10~(13)N m~(-1) for apeak subduction rate of 5cm a~(-1). In all cases considered, the rate of increase in negative buoyancy depends on the convergence rate at a particular period of time during subduction. If the velocity increases exponentially in the initial stages of subduction, the maximum rate of increase is observed when the slab subducts with the peak subduction velocity. If subduction continues with a constant velocity, the rate of increase in thermal buoyancy begins to decrease as the slab penetrates the lower mantle, and the buoyancy approaches an asymptotic value for increasing time. If the velocity decreases exponentially in the last stages of subduction, the negative buoyancy begins decreasing while the slab is still sinking, as its thermal anomaly decreases. After subduction stops, the slab achieves thermal equilibrium with the surrounding mantle in approximately 10-20 Ma depending on its past history.
机译：基于热模型和各种运动学边界条件，估算了俯冲洋板的负浮力。温度和负浮力均与时间有关，并且是根据随时间变化的俯冲率计算的。负浮力的大小随着板的穿透深度和俯冲速度的增加而增加。对于成熟的海洋岩石圈，当俯冲速率为5cm a〜（-1）时，到达地幔过渡带底部的平板浮力约为5 x 10〜（13）N m〜（-1）。在所有考虑的情况下，负浮力的增加速率取决于俯冲过程中特定时间的收敛速率。如果速度在俯冲的初始阶段呈指数增加，则当平板以最大俯冲速度俯冲时，观察到最大的增加速率。如果俯冲以恒定速度继续进行，则随着板块穿透下部地幔，热浮力的增加率开始降低，并且浮力随着时间的增加而逐渐接近渐近值。如果速度在俯冲的最后阶段呈指数下降，则负平板浮力将开始减小，而平板仍在下沉，因为其热异常减小。俯冲停止后，取决于其过去的历史，平板在大约10-20 Ma内与周围的地幔达到热平衡。

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